Melt polymerization of polycarbonate is typically achieved by reacting a bisphenol compound with a carbonate compound in a series of reactors in the presence of a catalyst. After the polymerization is complete, the catalyst is generally quenched (referred to herein as a quenched polycarbonate), and any additives are added to result in a polycarbonate composition. Polycarbonate compositions for media storage applications (such as CD, DVD, and BLU-RAY™ discs) produced by melt polycondensation processes typically experience quality issues, such as a reduction in the optical properties, when the catalyst is not quenched (referred to herein as an unquenched polycarbonate). This reduction in optical quality can ultimately reduce the applicability of unquenched polycarbonate for media storage applications.
The reduction in the optical properties in unquenched polycarbonate can occur due to the presence of active polymerization catalyst, which can catalyze the reactions between certain additives and the polycarbonate backbone. For example, mold release agents are typically added to quenched polycarbonate compositions to facilitate further processing of the resultant polycarbonate composition. In quenched polycarbonate, glycerol monostearate (GMS) and/or pentaerythritol tristearate (PETS) are typically added as the mold release agent. However, GMS molecules contain hydroxyl groups that can react with polycarbonate in the presence of an active catalyst, which results in a reduction in the optical properties such that the composition is not suitable for use as in media storage applications. PETS has been shown to have good stability in unquenched polycarbonate, but has also been shown to reduce the optical quality of discs molded therefrom.
An unquenched, melt polycarbonate composition comprising a mold release agent that could be used for media storage applications and a process of making the same is therefore desirable.